Vascular endothelial growth factor-C expression correlates with lymph node localization of human melanoma metastases

The lymphatic vasculature: An active and dynamic player in cancer progression

The lymphatic vasculature has been widely described and explored for its key functions in fluid homeostasis and in the organization and modulation of the immune response. Besides transporting immune cells, lymphatic vessels play relevant roles in tumor growth and tumor cell dissemination. Cancer cells that have invaded into afferent lymphatics are propagated to tumor‐draining lymph nodes (LNs), which represent an important hub for metastatic cell arrest and growth, immune modulation, and secondary dissemination to distant sites. In recent years many studies have reported new mechanisms by which the lymphatic vasculature affects cancer progression, ranging from induction of lymphangiogenesis to metastatic niche preconditioning or immune modulation. In this review, we provide an up‐to‐date description of lymphatic organization and function in peripheral tissues and in LNs and the changes induced to this system by tumor growth and progression. We will specifically focus on the reported interactions that occur between tumor cells and lymphatic endothelial cells (LECs), as well as on interactions between immune cells and LECs, both in the tumor microenvironment and in tumor‐draining LNs. Moreover, the most recent prognostic and therapeutic implications of lymphatics in cancer will be reported and discussed in light of the new immune‐modulatory roles that have been ascribed to LECs.

Functional interplay between secreted ligands and receptors in melanoma

Melanoma, the most aggressive form of skin cancer, results from the malignant transformation of melanocytes located in the basement membrane separating the epidermal and dermal skin compartments. Cutaneous melanoma is often initiated by solar ultraviolet radiation (UVR)-induced mutations. Melanocytes intimately interact with keratinocytes, which provide growth factors and melanocortin peptides acting as paracrine regulators of proliferation and differentiation. Keratinocyte-derived melanocortins activate melanocortin-1 receptor (MC1R) to protect melanocytes from the carcinogenic effect of UVR. Accordingly, MC1R is a major determinant of susceptibility to melanoma. Despite extensive phenotypic heterogeneity and high mutation loads, the molecular basis of melanomagenesis and the molecules mediating the crosstalk between melanoma and stromal cells are relatively well understood. Mutations of intracellular effectors of receptor tyrosine kinase (RTK) signalling, notably NRAS and BRAF, are major driver events more frequent than mutations in RTKs. Nevertheless, melanomas often display aberrant signalling from RTKs such as KIT, ERRB1-4, FGFR, MET and PDGFR, which contribute to disease progression and resistance to targeted therapies. Progress has also been made to unravel the role of the tumour secretome in preparing the metastatic niche. However, key aspects of the melanoma-stroma interplay, such as the molecular determinants of dormancy, remain poorly understood.

Lymphatic vessel density is associated with CD8+ T cell infiltration and immunosuppressive factors in human melanoma

Increased density of tumor-associated lymphatic vessels correlates with poor patient survival in melanoma and other cancers, yet lymphatic drainage is essential for initiating an immune response. Here we asked whether and how lymphatic vessel density (LVD) correlates with immune cell infiltration in primary tumors and lymph nodes (LNs) from patients with cutaneous melanoma. Using immunohistochemistry and quantitative image analysis, we found significant positive correlations between LVD and CD8+ T cell infiltration as well as expression of the immunosuppressive molecules inducible nitric oxide synthase (iNOS) and 2,3-dioxygénase (IDO). Interestingly, similar associations were seen in tumor-free LNs adjacent to metastatic ones, indicating loco-regional effects of tumors. Our data suggest that lymphatic vessels play multiple roles at tumor sites and LNs, promoting both T cell infiltration and adaptive immunosuppressive mechanisms. Lymph vessel associated T cell infiltration may increase immunotherapy success rates provided that the treatment overcomes adaptive immune resistance.

Targeting the VEGF-C/VEGFR3 axis suppresses Slug-mediated cancer metastasis and stemness via inhibition of KRAS/YAP1 signaling

Vascular endothelial growth factor-C (VEGF-C) has been implicated in epithelial-mesenchymal transition (EMT) processes and various human cancers, including skin cancer. Skin cancer is an aggressive human malignancy with increasing incidence worldwide; however, the underlying mechanisms involved in VEGF-C-induced skin cancer stemness and metastasis remain unclear. Here, we report that VEGF-C enhances skin cancer migration, invasion and stemness through Slug up-regulation. Oncomine database analysis indicated that the KRAS/MAPK (mitogen-activated protein kinases) pathway and YAP1 (yes-associated protein 1) expression are positively correlated with metastatic skin cancer. We show that VEGF-C triggers the activation of KRAS/MAPK signaling to increase YAP1 and downstream Slug expression, which are suppressed by an anti-VEGFR3 (VEGF receptor 3) peptide, a specific peptide targeting VEGFR3. The VEGF-C-induced migration, invasion and stemness of skin cancer cells are also abrogated by the anti-VEGFR3 peptide. Based on these data, we reveal the role of the VEGF-C/VEGFR3-mediated KRAS/MAPK-YAP1/Slug pathway in skin cancer progression and propose that the VEGF-C/VEGFR3 axis is a promising target for the anti-VEGFR3 peptide.

cIAP2 promotes gallbladder cancer invasion and lymphangiogenesis by activating the NF-κB pathway

Several studies have produced contradictory findings about the prognostic implications for inhibitor of apoptosis proteins (IAP) in different types of cancer. Cellular inhibitor of apoptosis 2 (cIAP2/BIRC) is one of the most extensively characterized human IAP. To date, no studies have focused on the expression level of cIAP2 in human gallbladder cancer (GBC), and the mechanism of cIAP2 in GBC invasion and lymphangiogenesis remains unclear. Therefore, in the present study, cIAP2 expression in GBC was detected using quantitative real‐time polymerase chain reaction and immunohistochemistry, and the relationship between cIAP2 levels in cancer tissues and the clinicopathological characteristics of patients was analyzed. The biological effect of cIAP2 in GBC cells was tested using the Cell Counting Kit‐8 Assay, Transwell assays and the ability of human dermal lymphatic endothelial cells (HDLEC) to undergo tube formation. The role of cIAP2 in activating the NF‐κB pathway was determined using a dual‐luciferase reporter assay, immunofluorescence staining, western blotting and ELISA. Finally, an animal model was used to further confirm the role of cIAP2 in lymphangiogenesis. We showed that cIAP2 expression was elevated in human GBC tissues and correlated with a negative prognosis for patients. Moreover, cIAP2 was identified as a lymphangiogenic factor of GBC cells and, thus, promoted lymph node metastasis in GBC cells. Our study is the first to suggest that cIAP2 can promote GBC invasion and lymphangiogenesis by activating the NF‐κB pathway.

Effects of fatty acid synthase inhibitors on lymphatic vessels: an in vitro and in vivo study in a melanoma model

Fatty acid synthase (FASN) is responsible for the endogenous production of fatty acids from acetyl-CoA and malonyl-CoA. Its overexpression is associated with poor prognosis in human cancers including melanomas. Our group has previously shown that the inhibition of FASN with orlistat reduces spontaneous lymphatic metastasis in experimental B16-F10 melanomas, which is a consequence, at least in part, of the reduction of proliferation and induction of apoptosis. Here, we sought to investigate the effects of pharmacological FASN inhibition on lymphatic vessels by using cell culture and mouse models. The effects of FASN inhibitors cerulenin and orlistat on the proliferation, apoptosis, and migration of human lymphatic endothelial cells (HDLEC) were evaluated with in vitro models. The lymphatic outgrowth was evaluated by using a murine ex vivo assay. B16-F10 melanomas and surgical wounds were produced in the ears of C57Bl/6 and Balb-C mice, respectively, and their peripheral lymphatic vessels evaluated by fluorescent microlymphangiography. The secretion of vascular endothelial growth factor C and D (VEGF-C and -D) by melanoma cells was evaluated by ELISA and conditioned media used to study in vitro lymphangiogenesis. Here, we show that cerulenin and orlistat decrease the viability, proliferation, and migration of HDLEC cells. The volume of lymph node metastases from B16-F10 experimental melanomas was reduced by 39% in orlistat-treated animals as well as the expression of VEGF-C in these tissues. In addition, lymphatic vessels from orlistat-treated mice drained more efficiently the injected FITC-dextran. Orlistat and cerulenin reduced VEGF-C secretion and, increase production of VEGF-D by B16-F10 and SK-Mel-25 melanoma cells. Finally, reduced lymphatic cell extensions, were observed following the treatment with conditioned medium from cerulenin- and orlistat-treated B16-F10 cells. Altogether, our results show that FASN inhibitors have anti-metastatic effects by acting on lymphatic endothelium and melanoma cells regardless the increase of lymphatic permeability promoted by orlistat.

Opposing Roles of JNK and p38 in Lymphangiogenesis in Melanoma

In primary melanoma, the amount of vascular endothelial growth factor C (VEGF-C) expression and lymphangiogenesis predicts the probability of metastasis to sentinel nodes, but conditions boosting VEGF-C expression in melanoma are poorly characterized. By comparative mRNA expression analysis of a set of 22 human melanoma cell lines, we found a striking negative correlation between VEGF-C and microphthalmia-associated transcription factor (MITF) expression, which was confirmed by data mining in GEO databases of human melanoma Affymetrix arrays. Moreover, in human patients, high VEGF-C and low MITF levels in primary melanoma significantly correlated with the chance of metastasis. Pathway analysis disclosed the respective c-Jun N-terminal kinase and p38/mitogen-activated protein kinase activities as being responsible for the inverse regulation of VEGF-C and MITF. Predominant c-Jun N-terminal kinase signaling results in a VEGF-C(low)/MITF(high) phenotype; these melanoma cells are highly proliferative, show low mobility, and are poorly lymphangiogenic. Predominant p38 signaling results in a VEGF-C(high)/MITF(low) phenotype, corresponding to a slowly cycling, highly mobile, lymphangiogenic, and metastatic melanoma. In conclusion, the relative c-Jun N-terminal kinase and p38 activities determine the biological behavior of melanoma. VEGF-C and MITF levels serve as surrogate markers for the respective c-Jun N-terminal kinase and p38 activities and may be used to predict the risk of metastasis in primary melanoma.

Significance of Vascular Endothelial Growth Factor (VEGF)-C and VEGF-D in the Progression of Cutaneous Melanoma

INTRODUCTION

Induction of tumor lymphangiogenesis by vascular endothelial growth factor (VEGF)-C and VEGF-D promotes metastasis in many human cancers.

AIM

The aim of this study was to examine the role of VEGF-C and VEGF-D in lymphangiogenesis and lymph node metastasis in patients with cutaneous melanoma.

MATERIALS AND METHODS

Fifty-four melanoma specimens (18 with lymph node metastasis, 36 nonmetastatic) were investigated by immunostaining for VEGF-C, VEGF-D, and for lymphatic endothelial marker D2-40. VEGF-C and VEGF-D expression was assessed as a percentage and intensity of stained tumor cells, tumor-associated macrophages and fibroblasts. The quantification of lymphangiogenesis was conducted by computer-assisted morphometric analysis.

RESULTS

The expressions of both VEGF-C and VEGF-D in tumor cells were significantly higher in lymph node metastatic melanomas compared with nonmetastatic melanomas (P = .015 VEGF-C; P = .005 VEGF-D). There was no statistically significant difference between metastatic and nonmetastatic melanomas regarding the expression of VEGF-C and VEGF-D in macrophages and fibroblasts. Metastatic melanomas showed a significantly higher intratumoral and peritumoral lymphatic vessel density (LVD) compared with nonmetastatic melanomas (P = .000 intratumoral, P = .000 peritumoral). Melanomas with VEGF-C positive tumor cells showed a significantly higher intratumoral and peritumoral LVD compared with VEGF-C negative tumor cells group of melanomas (P = .006 intratumoral, P = .010 peritumoral). VEGF-C expression in macrophages, fibroblasts, as well as VEGF-D expression in tumor cells, macrophages, and fibroblasts, showed no correlation with the intratumoral and peritumoral LVD.

CONCLUSIONS

Our findings show the significance of VEGF-C in tumor cells in the induction of intratumoral and peritumoral lymphangiogenesis. This study suggests that both VEGF-C and VEGF-D in tumor cells promote lymph node metastasis, and that the immunohistochemical analysis of expression can be a useful tool for predicting clinical behavior of cutaneous melanoma.

Blood microvessel density, lymphatic microvessel density and lymphatic invasion in predicting melanoma metastases: systematic review and meta-analysis

In malignant melanoma (MM) there is an urgent need to identify new markers with predictive value superior to the traditional clinical and histological parameters. Angiogenesis and lymphangiogenesis have been recognized as critical processes in tumour growth and metastasis development, and numerous studies have evaluated the significance of these parameters in predicting the prognosis in solid tumours, including MM. We set out to determine whether angiogenesis, lymphangiogenesis and lymphatic invasion (LI) are valuable prognostic markers in MM. We systematically reviewed the available literature and subsequently performed a meta-analysis on the compiled data. To be eligible for the systematic review, a study had to provide the microvessel density (MVD), the lymphatic vessel density (LVD) or information about LI, assessed by immunohistochemistry on the primary site in patients with MM. To be evaluable for the meta-analysis, a study also had to provide information on clinical outcome. We approached selected studies with the Reporting recommendations for tumour marker (REMARK) criteria, verifying whether they had followed the recommendations. In total, nine angiogenesis, seven lymphangiogenesis and 10 LI studies were included in our meta-analysis, representing 419, 474 and 802 patients, respectively. Using meta-analysis, we showed that peritumoral LVD and the presence of LI have prognostic value for patients with MM. In contrast, MVD and intratumoral LVD did not have prognostic value in these patients. LVD and LI seem to have prognostic value for patients with MM.

(Lymph)angiogenic influences on hematopoietic cells in acute myeloid leukemia

The purpose of this review is to provide an overview of the effect of (lymph)angiogenic cytokines on hematopoietic cells involved in acute myeloid leukemia (AML). Like angiogenesis, lymphangiogenesis occurs in pathophysiological conditions but not in healthy adults. AML is closely associated with the vasculature system, and the interplay between lymphangiogenic cytokines maintains leukemic blast survival in the bone marrow (BM). Once AML is induced, proangiogenic cytokines function as angiogenic or lymphangiogenic factors and affect hematopoietic cells, including BM-derived immune cells. Simultaneously, the representative cytokines, VEGFs and their receptors are expressed on AML blasts in vascular and osteoblast niches in both the BM and the peripheral circulation. After exposure to (lymph)angiogenic cytokines in leukemogenesis and infiltration, immune cell phenotypes and functions are affected. These dynamic behaviors in the BM reflect the clinical features of AML. In this review, we note the importance of lymphangiogenic factors and their receptors in hematopoietic cells in AML. Understanding the functional characterization of (lymph)angiogenic factors in the BM niche in AML will also be helpful in interrupting the engraftment of leukemic stem cells and for enhancing immune cell function by modulating the tumor microenvironment.

Impact of the prolymphangiogenic crosstalk in the tumor microenvironment on lymphatic cancer metastasis

Lymphangiogenesis is a very early step in lymphatic metastasis. It is regulated and promoted not only by the tumor cells themselves, but also by cells of the tumor microenvironment, including cancer associated fibroblasts, mesenchymal stem cells, dendritic cells, or macrophages. Even the extracellular matrix as well as cytokines and growth factors are involved in the process of lymphangiogenesis and metastasis. The cellular and noncellular components influence each other and can be influenced by the tumor cells. The knowledge about mechanisms behind lymphangiogenesis in the tumor microenvironmental crosstalk is growing and offers starting points for new therapeutic approaches.

Activin A is anti-lymphangiogenic in a melanoma mouse model

Melanoma spreads primarily to the sentinel lymph nodes, and its risk correlates with lymphangiogenesis, which is mainly driven by vascular endothelial growth factor (VEGF)-C. However, anti-lymphangiogenic factors are poorly characterized. We have shown in a melanoma model that Wnt1 reduces lymphangiogenesis by reducing VEGF-C expression. Screening this model for additional potentially anti-lymphangiogenic factors identified increased activin A expression and reduced expression of the antagonist, follistatin (FST), in Wnt1(+) cells. Activin A is known to reduce blood vessel formation, but the effects on lymphangiogenesis are unknown. Here we show that human primary melanoma expresses significantly higher levels of activin A and lower levels of FST compared with nevi and melanoma metastasis. Using our mouse model with melanoma cells overexpressing Wnt1, FST, Wnt1/FST, or the inhibin βA subunit (INHBA, resulting in activin A expression), we found both activin A and Wnt1 to reduce lymphangiogenesis. Whereas Wnt1 also reduced metastasis, this was not seen with activin A. In vitro, activin A phosphorylated SMAD2 in both melanoma and lymphatic endothelium but, although it reduced sprouting of lymphatic endothelium, it enhanced the migration of melanoma cells. In conclusion, activin A is an anti-lymphangiogenic factor, but because of its pleiotropic effects on cell mobility it appears not suitable as a pharmacological target.

Lymphangiogenesis: implications for diagnosis, treatment, and prognosis in patients with melanoma

Disease course in melanoma often cannot be accurately predicted by means of the prognostic factors usually considered in patients with melanoma; therefore, new factors are clearly needed. Increasingly robust scientific evidence shows that tumor lymph vessels play a key role in melanoma that metastasizes by lymphatic and hematogenous pathways. We review current knowledge and examine the implications of lymphangiogenesis in the diagnosis, treatment, and prognosis of patients with melanoma.

Lymphangiogenesis and lymphatic vessel remodelling in cancer

The generation of new lymphatic vessels through lymphangiogenesis and the remodelling of existing lymphatics are thought to be important steps in cancer metastasis. The past decade has been exciting in terms of research into the molecular and cellular biology of lymphatic vessels in cancer, and it has been shown that the molecular control of tumour lymphangiogenesis has similarities to that of tumour angiogenesis. Nevertheless, there are significant mechanistic differences between these biological processes. We are now developing a greater understanding of the specific roles of distinct lymphatic vessel subtypes in cancer, and this provides opportunities to improve diagnostic and therapeutic approaches that aim to restrict the progression of cancer.

Platelet-derived growth factor C and calpain-3 are modulators of human melanoma cell invasiveness

The molecular mechanisms responsible for the elevated metastatic potential of malignant melanoma are still not fully understood. In order to shed light on the molecules involved in the acquisition by melanoma of a highly aggressive phenotype, we compared the gene expression profiles of two cell clones derived from the human cutaneous metastatic melanoma cell line M14: a highly invasive clone (M14C2/MK18) and a clone (M14C2/C4) with low ability to invade the extracellular matrix (ECM). The highly invasive phenotype of M14C2/MK18 cells was correlated with overexpression of neuropilin-1, activation of a vascular endothelial growth factor (VEGF)-A/VEGFR-2 autocrine loop and secretion of matrix metalloprotease-2. Moreover, in an in vivo murine model, M14C2/MK18 cells displayed a higher growth rate as compared with M14C2/C4 cells, even though in vitro both clones possessed comparable proliferative potential. Microarray analysis in M14C2/MK18 cells showed a strong upregulation of platelet-derived growth factor (PDGF)-C, a cytokine that contributes to angiogenesis, and downregulation of calpain-3, a calcium-dependent thiol-protease that regulates specific signalling cascade components. Inhibition of PDGF-C with a specific antibody resulted in a significant decrease in ECM invasion by M14C2/MK18 cells, confirming the involvement of PDGF-C in melanoma cell invasiveness. Moreover, the PDGF-C transcript was found to be upregulated in a high percentage of human melanoma cell lines (17/20), whereas only low PDGF-C levels were detected in a few melanocytic cultures (2/6). By contrast, inhibition of calpain-3 activity in M14C2/C4 control cells, using a specific chemical inhibitor, markedly increased ECM invasion, strongly suggesting that downregulation of calpain-3 plays a role in the acquisition of a highly invasive phenotype. The results indicate that PDGF-C upregulation and calpain-3 downregulation are involved in the aggressiveness of malignant melanoma and suggest that modulators of these proteins or their downstream effectors may synergise with VEGF‑A therapies in combating tumour-associated angiogenesis and melanoma spread.

A quantitative examination of lymph drainage from perilesion skin in human melanoma

BACKGROUND

An increase in lymph flow from melanomas to draining lymph nodes has been reported in animal studies. It has been postulated that this contributes to metastatic potential of cancers. Data from animal studies are not easily extrapolated to humans; animal studies use immunosuppressed animals modified to overexpress lymphangiogenic growth factors, injected with human tumor cell lines, or manipulated to develop aggressive tumors. Human studies are required to investigate lymph flow in humans with cancers such as melanoma.

METHODS AND RESULTS

The present study aims to quantify the removal rate constant k (a measure of local lymph flow per unit volume of distribution of the radiotracer) from the vicinity of melanomas, benign nevi, and normal skin in humans in vivo using quantitative lymphoscintigraphy (QL). 16 patients with pigmented lesions underwent QL to quantify k near the lesion (k(perilesion)) and in contralateral matched normal skin (k(control)). The lesions were then excised and, based on histological outcome, the patients were divided into two groups: benign nevus (n=9) and melanoma (n=7). There was no difference between k(perilesion) and k(control) in either the benign naevus (p=0.29, paired t test) or the melanoma group (p=0.93). k(perilesion) in melanomas (0.233±0.123% min(-1)) was not increased relative to k(perilesion) in benign nevi (0.376±0.231% min(-1), p=0.16, unpaired t test).

CONCLUSIONS

We found no evidence for increased lymphatic drainage in melanoma relative to benign nevi or normal matched skin in humans.

Lymphatic biomarkers in primary melanomas as predictors of regional lymph node metastasis and patient outcomes

Recently developed lymphatic-specific immunohistochemical markers can now be utilized to assess intratumoral and/or peritumoral lymphatic vessel density (LVD), to detect lymphatic vessel invasion (LVI) by melanoma cells and to identify lymphatic marker expression in melanoma cells themselves. We systematically reviewed the available evidence for the expression of lymphatic markers as predictors of regional node metastasis and survival in melanoma patients. The currently available evidence suggests that LVD (particularly in a peritumoral location) and LVI are predictors of sentinel node metastasis and poorer survival. Nevertheless, adherence to international guidelines in the conduct and reporting of the studies was generally poor, with wide methodologic variations and heterogeneous findings. Larger, carefully conducted and well-reported studies that confirm these preliminary findings are required before it would be appropriate to recommend the routine application of costly and time-consuming immunohistochemistry for lymphatic markers in the routine clinical assessment of primary cutaneous melanomas.

Serum vascular endothelial growth factor (VEGF-C) as a diagnostic and prognostic marker in patients with ovarian cancer

VEGF-C is regarded as one of the most efficient factors in regulating lymphangiogenesis. The aim of this study was to better understand the role of VEGF-C in the progression of ovarian cancer and to assess its diagnostic and prognostic significance. A total of 109 patients with ovarian cancer, 76 patients with benign ovarian diseases, and 50 healthy controls were recruited in this study. Serum levels of VEGF-C were determined by ELISA method. The results showed that serum levels of VEGF-C were significantly higher in the patients with ovarian cancer than those with benign ovarian diseases and healthy controls (P<0.01). Serum level of VEGF-C was correlated with FIGO stage, lymph node metastasis, tumor resectability, and survival of the patients (P<0.05). The areas of receiver operating curves of VEGF-C were higher than those of CA125 in different screening groups. Analysis using the Kaplan-meier method indicated that patients with high VEGF-C had significantly shorter overall survival time than those with low VEGF-C (P<0.0001). In a multivariate analysis along with clinical prognostic parameters, serum VEGF-C was identified as an independent adverse prognostic variable for overall survival. These results indicated that serum VEGF-C may be a clinically useful indicator for diagnostic and prognostic evaluation in ovarian cancer patients.

Randomized, double-blind, placebo-controlled trial of sulindac in individuals at risk for melanoma: evaluation of potential chemopreventive activity

BACKGROUND

Reduced melanoma risk has been reported with regular use of nonsteroidal anti-inflammatory drugs (NSAIDs). However, the ability of NSAIDs to reach melanocytes in vivo and modulate key biomarkers in preneoplastic lesions such as atypical nevi has not been evaluated.

METHODS

This randomized, double-blind, placebo-controlled trial of sulindac was conducted in individuals with atypical nevi (AN) to determine bioavailability of sulindac and metabolites in nevi and effect on apoptosis and vascular endothelial growth factor A (VEGFA) expression in AN. Fifty subjects with AN ≥ 4 mm in size and 1 benign nevus (BN) were randomized to sulindac (150 mg twice a day) or placebo for 8 weeks. Two AN were randomized for baseline excision, and 2 AN and BN were excised after intervention.

RESULTS

Postintervention sulindac, sulindac sulfone, and sulindac sulfide concentrations were 0.31 ± 0.36, 1.56 ± 1.35, and 2.25 ± 2.24 μg/mL in plasma, and 0.51 ± 1.05, 1.38 ± 2.86, and 0.12 ± 0.12 μg/g in BN, respectively. Sulindac intervention did not significantly change VEGFA expression but did increase expression of the apoptotic marker cleaved caspase-3 in AN (increase of 3 ± 33 in sulindac vs decrease of 25 ± 45 in the placebo arm, P = .0056), although significance was attenuated (P = .1103) after adjusting for baseline expression.

CONCLUSIONS

Eight weeks of sulindac intervention resulted in high concentrations of sulindac sulfone, a proapoptotic metabolite, in BN but did not effectively modulate VEGFA and cleaved caspase-3 expression. Study limitations included limited exposure time to sulindac and the need to optimize a panel of biomarkers for NSAID intervention studies.

Tumor location and nature of lymphatic vessels are key determinants of cancer metastasis

Tumor metastasis to lymph nodes is a key indicator of patient survival, and is enhanced by the neo-lymphatics induced by tumor-secreted VEGF-C or VEGF-D, acting via VEGFR-3 signalling. These targets constitute important avenues for anti-metastatic treatment. Despite this new understanding, clinical observations linking metastasis with tumor depth or location suggest that lymphangiogenic growth factors are not the sole determinants of metastasis. Here we explored the influence of tumor proximity to lymphatics capable of responding to growth factors on nodal metastasis in a murine VEGF-D over-expression tumor model. We found that primary tumor location profoundly influenced VEGF-D-mediated lymph node metastasis: 89 % of tumors associated with the flank skin metastasised, in contrast with only 19 % of tumors located more deeply on the body wall (p < 0.01). Lymphatics in metastatic tumors arose from small lymphatics, and displayed distinct molecular and morphological profiles compared with those found in normal lymphatics. Smaller lymphatic subtypes were more abundant in skin (2.5-fold, p < 0.01) than in body wall, providing a richer source of lymphatics for VEGF-D(+) skin tumors, a phenomenon also confirmed in human samples. This study shows that the proximity of a VEGF-D(+) primary tumor to small lymphatics is an important determinant of metastasis. These observations may explain why tumor location relative to the lymphatic network is prognostically important for some human cancers.

Expression of vascular endothelial growth factor-C in primary cutaneous melanoma predicts sentinel lymph node positivity

BACKGROUND

Vascular endothelial growth factor-C (VEGF-C), a lymphatic vessel growth factor, has been involved in the formation of lymph nodal metastases in different tumor types. Early evidences indicate that VEGF-C expression in human primary melanoma could be predictive of lymph nodal metastases, whereas the role of lymphangiogenesis is still controversial.

METHODS

By immunohistochemical analysis, we investigated VEGF-C or CC chemokine receptor 7 expression, together with the lymphatic and blood vessel network, in 36 patients with primary skin melanomas and metastases at the sentinel lymph node biopsy (SLN-positive), and 26 melanoma patients with negative SLN biopsy (SLN-negative).

RESULTS

We found that VEGF-C expression in primary melanoma specimens was significantly associated with SLN-positive (p < 0.001), particularly in thin melanomas. An association between augmented peritumoral lymphatic vessel area and SLN-positive (p < 0.02) was also seen. Conversely, no association between either expression of the CC chemokine receptor 7 in the primary tumor, or intratumoral lymphatic vessel or peritumoral and intratumoral blood vessel area, and SLN-positive was found.

CONCLUSIONS

Our results, taking into account the expression of either VEGF-C or related histopathological markers, indicated the possibility to use VEGF-C immunohistochemistry as a marker of metastatic progression, especially in thin cutaneous melanomas.

Regional lymphatic immunity in melanoma

Melanoma is an immunogenic tumor that has developed methods to successfully evade immune recognition, while paradoxically spreading through the lymphatic system. Increasing evidence supports that melanoma-derived factors suppress regional immunity within the host. At a very early stage, melanoma communicates with the tumor-draining lymph nodes, and prepares them for seeding of metastatic disease by stimulating lymphangiogenesis and downregulation of the sentinel lymph node immunity well before the malignant cells arrive. Investigations have demonstrated that the induction of suppressor cells, peripheral tolerance, and a less tumor-responsive Th2 cytokine environment may provide a hospitable environment for subsequent lymphatic metastasis. Patients with early-stage disease may benefit from the restoration of the regional immune function to a level that controls the progression of residual occult metastases and ensures a durable clinical response. Herein we provide a succinct summary of the current progress in this field in order to guide future investigations.

Wnt1 is anti-lymphangiogenic in a melanoma mouse model

Wnt signals contribute to melanoma progression by boosting their proliferation and survival. Initially, we expected that activated Wnt signaling also improves their proficiency to recruit blood and lymph vessels. To assess this, we added cell culture supernatants (SNs) of Wnt1(+) and Wnt1(-) melanoma to endothelial spheroids. Whereas SNs of Wnt1(-) melanoma cells induced lymphatic sprouts, those of Wnt1(+) cells were unable to do so and this was restored by vascular endothelial growth factor C (VEGF-C). Subsequent testing of several human melanoma lines revealed that Wnt1 suppressed their VEGF-C expression. This Wnt1 effect did not depend on glycogen synthase kinase-3β (GSK3β), β-catenin, or activator protein-1, but was blocked by cyclosporine A (CsA). To analyze Wnt1 effects in melanoma in vivo, we selected Wnt1(-) melanoma cell lines, overexpressed Wnt1, and injected them subepidermally into severe combined immunodeficient (SCID) mice. We found reduced VEGF-C expression, reduced lymphangiogenesis, and delayed metastasis to sentinel nodes in Wnt1(+) as compared with Wnt1(-) melanoma (P<0.05). Concomitant overexpression of VEGF-C or feeding of animals with CsA restored lymphangiogenesis and metastasis in Wnt1(+) melanoma. In conclusion, Wnt1 is anti-lymphangiogenic by suppressing melanoma-derived VEGF-C expression.

MET expression in melanoma correlates with a lymphangiogenic phenotype

Melanomas contain high frequencies of tumorigenic cells and their tumorigenic capacity resides in several distinct subpopulations within melanoma. Since their metastatic potential is linked to their ability to recruit lymphatic vessels, we aimed at identifying lymphangiogenic subpopulations by comparative in vitro analysis of single cell clones derived from a melanoma of a single patient. Selected lymphangiogenic clones were then grafted into severe combined immunodeficient mice, where they induced lymphangiogenesis and metastasized into sentinel nodes, whereas non-lymphangiogenic clones from the same patient did not metastasize. Transcriptome analysis revealed high expression of vascular endothelial growth factor C (VEGF-C) and platelet derived growth factor C (PDGF-C) as well as of the met proto-oncogene (MET) and its targets to be associated with this lymphangiogenic phenotype. Screening of a set of independently isolated melanoma cell lines from other patients confirmed this association between expression of high levels of MET and of VEGF-C and PDGF-C. Hence, we provide a model to screen for the lymphangiogenic potential of tumor cells. We show that the lymphangiogenic potential is heterogeneously distributed among melanoma cells within one given tumor and is associated with activation of MET signaling.

Tumor-derived VEGF-C, but not VEGF-D, promotes sentinel lymph node lymphangiogenesis prior to metastasis in breast cancer patients

Breast cancer usually initially metastases to the sentinel lymph nodes (SLNs). Recent studies have demonstrated that tumor cells induce SLN lymphangiogenesis before metastasis in several malignancies. In addition, tumor-derived VEGF-C or VEGF-D may induce lymphangiogenesis and promote lymph node metastasis. To explore the mechanisms of lymph node metastasis in breast cancer, we investigated whether primary tumors induce SLN lymphangiogenesis before metastasis and determined the function of tumor-derived VEGF-C and VEGF-D in SLN lymphangiogenesis. Expression of VEGF-C and VEGF-D was examined using immunohistochemistry in 63 primary breast tumors. No significant relationships between VEGF-C and VEGF-D (P=0.420), and VEGF-C or VEGF-D expression and clinical parameters (age, tumor size, grade, hormonal receptor status, her-2 status) were observed (P>0.05). Expression of the lymphatic-specific markers VEGFR-3, Prox-1 and LYVE-1 was measured using quantitative real-time RT-PCR in uninvolved SLNs from 63 patients and compared to control lymph nodes from patients with benign breast disease. Expression of Prox-1 and LYVE-1 mRNA was significantly higher in uninvolved SLNs from breast cancer patients than that in control lymph nodes (P<0.01). Interestingly, expression of VEGFR-3, Prox-1 and LYVE-1 was significantly higher in SLNs from patients with high VEGF-C-expressing tumors than low VEGF-C-expressing tumors (P<0.05), but not VEGF-D-high-expressing tumors (P>0.05). This study demonstrates that primary breast tumors induce SLN lymphangiogenesis before metastasis occurs and that tumor-derived VEGF-C, but not VEGF-D, plays an important role in SLN lymphangiogenesis in breast cancer.

Semaphorin signaling in angiogenesis, lymphangiogenesis and cancer

Angiogenesis, the formation of new blood vessels from preexisting vasculature, is essential for many physiological processes, and aberrant angiogenesis contributes to some of the most prevalent human diseases, including cancer. Angiogenesis is controlled by delicate balance between pro- and anti-angiogenic signals. While pro-angiogenic signaling has been extensively investigated, how developmentally regulated, naturally occurring anti-angiogenic molecules prevent the excessive growth of vascular and lymphatic vessels is still poorly understood. In this review, we summarize the current knowledge on how semaphorins and their receptors, plexins and neuropilins, control normal and pathological angiogenesis, with an emphasis on semaphorin-regulated anti-angiogenic signaling circuitries in vascular and lymphatic endothelial cells. This emerging body of information may afford the opportunity to develop novel anti-angiogenic therapeutic strategies.

Expression of the soluble vascular endothelial growth factor receptor-1 in cutaneous melanoma: role in tumour progression

BACKGROUND

Vascular endothelial growth factor (VEGF)-A, placenta growth factor (PlGF) and their corresponding membrane receptors are involved in autocrine and paracrine regulation of melanoma growth and metastasis. Besides the membrane receptors, a soluble form of the VEGF receptor (VEGFR)-1 (sVEGFR-1) has been identified, that behaves both as a decoy receptor, sequestering VEGF-A and PlGF, and as an extracellular matrix (ECM) molecule, promoting endothelial cell adhesion and migration through the interaction with α5β1 integrin.

OBJECTIVES

To analyse whether sVEGFR-1 plays a role during melanoma progression.

METHODS

sVEGFR-1 expression was evaluated in a panel of 36 melanoma cell lines and 11 primary human melanocyte cultures by quantitative real-time polymerase chain reaction analysis and in specimens of primary or metastatic melanoma lesions from 23 patients by immunohistochemical analysis.

RESULTS

sVEGFR-1 expression was highly upregulated in melanoma cell lines with respect to human melanocytes. Interestingly, cell lines obtained from cutaneous metastases showed a significant reduction of sVEGFR-1 expression, as compared with cell lines derived from primary tumours. These results were confirmed by immunohistochemical analysis of sections from primary skin melanomas and the corresponding cutaneous metastases, suggesting that modulation of sVEGFR-1 expression influences ECM invasion by melanoma cells and metastasis localization. Moreover, we provide evidence that adhesion of melanoma cells to sVEGFR-1 is favoured by the activation of a VEGF-A/VEGFR-2 autocrine loop.

CONCLUSIONS

Our data strongly suggest that sVEGFR-1 plays a role in melanoma progression and that low sVEGFR-1/VEGF-A and sVEGFR-1/transmembrane VEGFR-1 ratios might predict a poor outcome in patients with melanoma.

Inflammation and tumor microenvironment in lymph node metastasis

In nearly all human cancers, the presence of lymph node (LN) metastasis increases clinical staging and portends worse prognosis (compared to patients without LN metastasis). Herein, principally reviewing experimental and clinical data related to malignant melanoma, we discuss diverse factors that are mechanistically involved in LN metastasis. We highlight recent data that link tumor microenvironment, including inflammation (at the cellular and cytokine levels) and tumor-induced lymphangiogenesis, with nodal metastasis. Many of the newly identified genes that appear to influence LN metastasis facilitate general motility, chemotactic, or invasive properties that also increase the ability of cancer cells to disseminate and survive at distant organ sites. These new biomarkers will help predict clinical outcome and point to novel future therapies in metastatic melanoma as well as other cancers.

Biomarkers of metastatic melanoma

Melanoma, one of the most aggressive forms of human cancer, has undergone an alarming increase in incidence in recent years. Early detection is a prerequisite for proper diagnosis and therapy orientation. Soluble biomarkers are an important tool for early diagnosis. Markers that are associated with melanocyte functions imply the enzymes involved in melanin synthesis and the melanin-related metabolites. Proteins such as autocrine melanocyte cell growth factor and melanoma metastasis suppressor have gained attention in the biomarkers domain. The antimelanoma immune response elicited in patients can not only provide new biomarkers but important therapeutic approaches in specific treatments. All the molecules generated during the metastasis process, invasion of neighboring tissue, angiogenesis, invading lymphatic/blood vessels and establishing new tumors at a distant site, are targets for biomarker discovery.

Serum VEGF-C is associated with metastatic site in patients with malignant melanoma

Vascular endothelial growth factor-C (VEGF-C) is involved in lymphatic metastatic spread. Metastatic site is a prognostic factor in melanoma. We assessed whether serum levels of VEGF-C are associated with metastatic sites or prognosis in patients treated for stage IV melanoma. The study included 64 patients, who received dacarbazine or four-drug chemotherapy (dacarbazine, vincristine, bleomycin and lomustine; BOLD) both combined with interferon-alfa. Serum samples for VEGF-C were analyzed by ELISA. The patients (n =22) with only skin and subcutaneous metastases had significantly lower mean VEGF-C levels (1 643 pg/ml) then the patients (n =42) with other distant metastases (2 584 pg/ml, Mann-Whitney, p =0.033). VEGF-C levels above the median (1 590 pg/ml) were significantly related to deep lymph node involvement (OR 3.763; 95% CI 1.038 - 13.646, p =0.034). There were no other significant associations between VEGF-C levels and tumour burden, nor were the levels significantly related to the response to therapy or survival. Those eight patients, who had received previous adjuvant IFN-alfa therapy had lower mean VEGF-C levels (1 738 pg/ml) as compared to those 56 patients without previous IFN-alfa therapy (2 335 pg/ml, ANOVA, p =0.026). This is the first study exploring serum VEGF-C in melanoma. VEGF-C might be involved in the deep lymphatic dissemination and progression of melanoma metastasis.

High VEGFR-3-positive circulating lymphatic/vascular endothelial progenitor cell level is associated with poor prognosis in human small cell lung cancer

PURPOSE

The newly identified bone marrow-derived cell population, called lymphatic/vascular endothelial progenitor cells (LVEPC), has been shown to contribute to lymph capillary growth in experimental tumor systems. The clinical significance of these cells has not yet been investigated in a human malignancy. Our aim was to study whether peripheral blood circulating LVEPCs participate in the progression of human small cell lung cancer (SCLC).

EXPERIMENTAL DESIGN

A total of 88 patients with limited-stage SCLC and 32 tumor-free control subjects were included. Peripheral blood circulating LVEPC labeled with CD34 and vascular endothelial growth factor receptor-3 (VEGFR3) antibodies and the serum levels of the key lymphangiogenic molecule VEGF-C were measured by flow cytometry and ELISA, respectively.

RESULTS

CD34-positive/VEGFR3-positive LVEPC levels were significantly increased in patients (versus controls; P<0.01), and there was also a significant relationship between LVEPC counts and lymph node metastasis (P<0.01). High pretreatment circulating LVEPC numbers correlated with poor overall survival (P<0.01). Although we observed significantly elevated VEGF-C concentrations in patients (versus controls; P<0.01), there was no significant correlation between VEGF-C and LVEPC levels. Moreover, no significant differences in peripheral blood VEGF-C levels were seen between patients subgrouped by clinicopathologic variables including tumor and lymph node stages and survival.

CONCLUSIONS

Peripheral blood levels of bone marrow-derived LVEPCs are significantly increased in patients with SCLC and correlate with lymphatic involvement and prognosis. This is the first study that shows evidence of increased numbers of circulating LVEPC in patients with a malignant tumor.

Tumour Angiogenesis, Vascular Biology and Enhanced Drug Delivery

It is now common knowledge that for a solid tumour to become life-threatening clinically, an adequate blood supply to the neoplasm has to be established. Although neovascularisation via angiogenesis leads to a subsequent rapid growth of the tumour mass, it provides the most reliable route by which neoplastic cells may be reached by cytotoxics. In addition, for a majority of tumours, the lesion's vasculature is more permeable and tortuous than that of the surrounding healthy host tissue. Such deviation potentiates selective delivery of drugs to be achieved. This review examines, from various viewpoints, the area of tumour angiogenesis and vascularisation, currently one of the most fertile and active fields of cancer research.

The role of VEGF-C staining in predicting regional metastasis in melanoma

Sentinel lymph node status is the most important prognostic factor in primary melanoma. The number of melanoma-associated lymphatic vessels has been associated with sentinel lymph node status and survival. Vascular endothelial growth factor-C (VEGF-C) is found to promote tumour-associated lymphatic vessel growth. In many human neoplasms, VEGF-C expression in neoplastic cells or tumour-associated macrophages (TAMs) has been linked to lymphatic dissemination of tumour cells. Recent studies have suggested a correlation between VEGF-C expression in primary melanoma and the presence of lymph node metastasis. We performed VEGF-C immunohistochemical staining on melanoma tissues of 113 patients with known sentinel lymph node status. We showed that both high VEGF-C expression in melanoma cells and TAMs are positively associated with the presence of a positive sentinel lymph node. No correlation with Breslow thickness, Clark invasion level or ulceration could be detected. VEGF-C expression in melanoma cells was predictive of a shorter overall and disease-free survival, without being an independent predictor of survival. Our results confirm that VEGF-C expression in primary cutaneous melanoma plays a role in the lymphatic spread of the tumour.

Tumor lymphangiogenesis and melanoma metastasis

Malignant melanomas of the skin primarily metastasize to lymph nodes, and the detection of sentinel lymph node metastases serves as an important prognostic parameter. There is now compelling evidence that melanomas can induce lymphangiogenesis (growth of lymphatic vessels), mainly at the tumor-stroma interface, and that the level of tumor lymphangiogenesis is correlated with the incidence of sentinel lymph node metastases and with disease-free survival. Thus, tumor lymphangiogenesis can serve as a novel prognostic predictor in melanoma. Vascular endothelial growth factor (VEGF)-C, released by melanoma cells and by tumor-associated macrophages, likely represents the major lymphangiogenic factor in melanoma, although other members of the VEGF family might also be involved. The recent discovery that tumors can induce a premetastatic niche, by inducing lymphatic vessel growth in sentinel lymph nodes even before metastasis, and that lymph node lymphangiogenesis enhances metastatic spread, indicates that activated lymphatic vessels represent novel targets for the detection and/or therapy of melanoma metastases.

(+)-Catechin inhibits tumour angiogenesis and regulates the production of nitric oxide and TNF-α in LPS-stimulated macrophages

The anti-angiogenic activity of (+)-catechin as well as its regulatory effect on the production of nitric oxide and TNFα were studied using in vivo and in vitro models. In vivo angiogenic activity was studied using B16F-10 melanoma cell-induced capillary formation in C57BL/6 mice. Administration of (+)-catechin significantly inhibited (36.09%) the number of tumour-directed capillaries induced by injecting B16F-10 melanoma cells on the ventral side of C57BL/6 mice. The cytokine profile in the serum of these animals showed a drastically increased level of proinflammatory cytokines such as IL-1β, IL-6, TNF-α, GM-CSF and the direct endothelial cell proliferating agent, VEGF. Administration of (+)-catechin could differentially regulate elevation of these cytokines. The differential elevation is further evidenced by the increased production of IL-2 and tissue inhibitor of metalloproteinase-1 (TIMP-1) in the B16F-10 injected, (+)-catechin-treated animals. In vitro L929 bioassay revealed the inhibition of TNF-α production by (+)-catechin treatment. In the rat aortic ring assay, (+)-catechin inhibited the microvessel outgrowth at non-toxic concentrations. (+)-Catechin at non-toxic concentrations (5—25 µg/ml) showed significant inhibition in the proliferation, migration and tube formation of endothelial cells, which are the key events in the process of angiogenesis. (+)-Catechin also showed inhibitory effect on VEGF mRNA levels in B16F-10 melanoma cells. (+)-Catechin inhibited the production of NO and TNF-α in LPS-stimulated primary macrophages. Taken together, these results demonstrate that (+)-catechin inhibits tumour-specific angiogenesis by regulating the production of pro- and anti-angiogenic factors such as pro-inflammatory cytokines, nitric oxide, VEGF, IL-2 and TIMP-1. These results also suggest that (+)-catechin could significantly inhibit nitrite and TNF-α production in LPS-stimulated macrophages.

Lymphangiogenesis induced by VEGF-C and VEGF-D promotes metastasis and a poor outcome in breast carcinoma: a retrospective study of 61 cases

PURPOSE

To evaluate lymphangiogenesis in patients with breast carcinoma, explore the underlying mechanism, and study the relationship between lymphangiogenesis and progression of breast carcinoma.

METHODS

Sixty-one cases of breast carcinoma with complete clinical and pathological data were analyzed. Using an anti-podoplanin monoclonal antibody, an immunohistochemical study was made of all specimens to detect lymphatic vessel density (LVD) and to investigate its clinicopathological and prognostic value. VEGF-C and VEGF-D were observed by RT-PCR and immunostaining to investigate their clinicopathological and prognostic values and their relationship with lymphangiogenesis.

RESULTS

LVD in breast carcinoma (6.28+/-3.73) was significantly higher than in benign mammary lesions (0.50+/-1.27), P<0.01 and was significantly associated with lymphatic metastasis and high TNM stage, P<0.01. The level of VEGF-C and VEGF-D expression was also significantly higher in breast carcinomas than in benign mammary lesions, P<0.01. LVD increased significantly with higher expression of VEGF-C and VEGF-D, P<0.01. Patients with high expression of VEGF-C and VEGF-D were observed to be more likely to have a bad outcome, P<0.05.

CONCLUSIONS

Lymphangiogenesis was significantly associated with lymph node metastasis, high TNM, and poor outcome in breast carcinoma. LVD may serve as a predictor of lymph node metastasis and a prognostic factor in breast carcinoma. VEGF-C and VEGF-D play an important role in lymphangiogenesis making the carcinoma more aggressive and leading to a poor prognosis.

A phase II study of ABT-510 (thrombospondin-1 analog) for the treatment of metastatic melanoma

OBJECTIVES

Thrombospondins are natural inhibitors of angiogenesis, tumor metastases, and tumor growth (melanoma). ABT-510 is a synthetic analog of thrombospondin-1, well tolerated in phase I studies. We conducted a phase II trial evaluating the clinical efficacy of ABT-510 and its effects on biomarkers of angiogenesis and immunity in patients with metastatic melanoma (MM).

PATIENTS AND METHODS

A 2-stage phase II clinical trial was conducted to assess the clinical efficacy, safety, and pharmacodynamic effects (angiogenesis and immunity) of ABT-510 in patients with stage IV melanoma. The primary endpoint was 18-week treatment failure rate. Patients self-administered 100 mg of ABT-510 subcutaneously twice daily. Blood samples were collected at baseline and every 3 weeks while on therapy. Eligible patients demonstrated measurable disease, good performance status and no evidence of intracranial metastases. Correlative laboratory studies evaluated biomarkers of angiogenesis and immunity.

RESULTS

Twenty-one patients were enrolled. Most patients were stage M1c (71%) and all had prior therapy for MM. Only 3 of the first 20 patients enrolled were progression free and on treatment at 18 weeks resulting in early termination of the study. Decreases in peripheral blood VEGF-A levels and VEGF-C levels, and CD146 and CD34/133 counts relative to pretreatment were detected. Limited changes in antitumor T cell immunity were observed.

CONCLUSIONS

ABT-510 therapy administered at 100 mg twice/day in patients with MM did not demonstrate definite clinical efficacy. Further dose escalation or combination with cytotoxic therapy may be more effective therapeutically.